This type of process is known for example from documents U.S. Pat. No. 5,417,975 and WO96/12509. More specifically, document U.S. Pat. No. 5,417,975 discloses the preparation of well-known bone regeneration material of natural origin, Bio-Oss®, and document WO96/12509 discloses the preparation of osteoconductive material.
Aside from the improved osteoconductive properties of natural bone regeneration material, the production thereof also allows recovery of butcher and slaughterhouse organic waste which forms a low-cost source having abundant bone material.
In the process of U.S. Pat. No. 5,417,975 the bone material is first degreased and then placed in a heated aqueous solution of primary amines or ammonia, preferably to a temperature between 80 and 200° C., wherein the organic substances are degraded and solubilized for final extraction by successive rinsing in demineralized water preferably heated to a temperature of between 20 and 60° C. at a water-flow rate advantageously of at least 10 cm per hour.
Degreasing is obtained by immersing the bone material in an organic solvent such as toluene or methylcyclohexane heated under reflux at a temperature of between 80 and 120° C.
According to U.S. Pat. No. 5,417,975 the contacting time between the bone material and the heated aqueous solution is dependent on the particle size of the material, on the reactivity of primary amines or ammonia solution and on the temperature to which this aqueous solution is heated. In general, this time is between 2 and 200 hours. For example, a bone material sample 1 cm in diameter treated with an aqueous ethylene diamine solution at 118° C. requires a treatment time of at least 50 hours to obtain satisfactory degradation of organic substances so that after rinsing their remaining content is lower than 150 ppm.
The bone material thus treated is then air dried at temperatures between 250° C. and 600° C. until the weight of the material stabilizes at a constant value. To obtain high purity bone regeneration material i.e. in which the organic substance content is lower than 150 ppm, the rinsing step with demineralized water must be performed continuously over a period ranging from 5 to 25 days.
Unfortunately the process suffers from several limitations. First it entails treatment using organic solvents the residues of which after treatment cannot be recycled and must be treated. Next this process involves treatment in an amine bath at 60° C. for more than 50 hours followed by rinsing in continuously flowing demineralized water over a period of at least 5 days. Clearly the lengthy time of the process (at least 5 days), moreover involving use of polluting organic products which must be treated, means that the process on industrial scale is costly and difficult to amortize.